1. Field of the Invention
The present invention relates to a process for preparing zeolites having the MTT framework topology defined by the connectivity of the tetrahedral atoms in the zeolite using the following structure directing agent:
                N,N,N,N′N′N′-Hexamethyl-propane-1,3-diammonium cation.        
2. State of the Art
Zeolites having the MTT framework topology defined by the connectivity of the tetrahedral atoms (referred to herein simply as MTT) are known. See, for example, Ch. Baerlocher et al., Atlas of Zeolite Framework Types, 5th Revised Edition, 2001 of the International Zeolite Association. Examples of MTT zeolites include the zeolite designated “SSZ-32”. SSZ-32 and methods for making it are disclosed in U.S. Pat. No. 5,053,373, issued Oct. 1, 1991 to Zones. This patent discloses the preparation of zeolite SSZ-32 using in N-lower alkyl-N′-isopropylimidazolium cation as an organic structure directing agent (SDA), sometimes called a templating agent. U.S. Pat. No. 4,076,842, issued Feb. 28, 1978 to Plank et al., discloses the preparation of the zeolite designated “ZSM-23”, a zeolite with a structure similar to SSZ-32, using a cation derived from pyrrolidine as the SDA. Zeolites SSZ-32 and ZSM-23 are commonly referred to as having the MTT framework topology. Both of the aforementioned patents are incorporated herein by reference in their entirety. Other MTT zeolites include EU-13, ISI-4 and KZ-1.
U.S. Pat. No. 5,707,600, issued Jan. 13, 1998 to Nakagawa et al., discloses a process for preparing medium pore size zeolites, including SSZ-32, using small, neutral amines. The amines contain (a) only carbon, nitrogen and hydrogen atoms, (b) one primary, secondary or tertiary, but not quaternary, amino group, and (c) a tertiary nitrogen atom, at least one tertiary carbon atom, or a nitrogen atom bonded directly to at least one secondary carbon atom, wherein the process is conducted in the absence of a quaternary ammonium compound. Examples of the small amines include isobutylamine, diisobutylamine, trimethylamine, cyclopentylamine, diisopropylamine, sec-butylamine, 2,5-dimethylpyrrolidine and 2,6-dimethylpiperidine.
U.S. Pat. No. 5,707,601 issued Jan. 13, 1998 to Nakagawa, discloses a process for preparing MTT zeolites using small, neutral amines. The amines contain (a) only carbon, nitrogen and hydrogen atoms, (b) one primary, secondary, or tertiary, but not quaternary, amino group, and (c) a tertiary nitrogen atom, at least one tertiary carbon atom, or a nitrogen atom bonded directly to at least one secondary carbon atom, wherein the process is conducted in the absence of a quaternary ammonium compound. Examples of the small amines include isobutylamine, diisobutylamine, trimethylamine, cyclopentylamine, diisopropylamine, sec-butylamine, 2,5-dimethylpyrrolidine and 2,6-dimethylpiperidine.
U.S. Pat. No. 5,785,947, issued Jul. 28, 1998 to Zones et al., discloses that zeolites, including medium pore size, unidimensional zeolites, can be prepared using a mixture of an amine component comprising (1) at least one amine containing one to eight carbon atoms, ammonium hydroxide, and mixtures thereof, and (2) an organic templating compound capable of forming the zeolite in the presence of the amine component, wherein the amine is smaller than the organic templating compound. Examples of the amines include isopropylamine, isobutylamine, n-butylamine, piperidine, 4-methylpiperidine, cyclohexylamine, 1,1,3,3-tetramethylbutylamine and cyclopentylamine and mixtures of such amines.
U.S. Pat. No. 5,332,566, issued Jul. 26, 1994 to Moini, discloses a method of synthesizing ZSM-23 (i.e., MTT) using an organic directing agent having the structure:

U.S. Pat. No. 6,475,464, issued Nov. 5, 2002 to Rouleau et al., discloses the preparation of MTT zeolites using alkylated polymethylene α-ω diammonium derivatives acting as a template or structure directing agent. These derivatives are defined by the formula R1R2R3N+(CH2)nN+R4R5R6, n being in the range 3 to 14 and R1 to R6, which may be identical or different, representing alkyl or hydroxylalkyl radicals containing 1 to 8 carbon atoms; up to five R1 to R6 radicals can be hydrogen. N,N,N,N′,N′N′-hexamethyl-propane-1,3-diammonium dication is not specifically disclosed, nor is it used in any of the examples. It is disclosed that the MTT zeolite may be prepared using alkali metal or ammonium ion. Sodium or ammonium cations are used in the examples. It is also required that the reaction mixture contain seed crystals of a zeolite other than a MTT zeolite.
It has now been found that MTT zeolites, such as SSZ-32, can be prepared using structure directing agent N,N,N,N′,N′N′-hexamethyl-propane-1,3-diammonium dication.